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Vid Famous crazycraft company Aerovironment has won a $2.1m contract to further develop its robotic "Nano Air Vehicle" (NAV), which flies and hovers using flapping wings like a hummingbird. The company has also released a video of the innovative craft in test flights.

According to Aerovironment, the fluttering NAV achievement is the first ever "controlled hovering flight of an air vehicle system with two flapping wings that carries its own energy source and uses only the flapping wings for propulsion and control".

The NAV project is one of the swarming brainchildren of DARPA, the Pentagon tech-wizardry bureau. Many of DARPA's spawnings don't make it past Phase 1; the new Phase 2 deal with Aerovironment indicates a somewhat greater chance of eventual success.

Such a success, according to DARPA's Dr Todd Hylton, would see the tiny ornithopter shrink to 10 grams' weight and a maximum size of 7.5cm. The little machine, to meet the US government's requirements, must also achieve forward-flight speeds of 10 metres per second (22 mph) and be able to resist gentle gusts of wind in the hover. It must also become quieter.

The hummingbird- or large-insect-sized craft is intended by DARPA for clandestine "urban mission operations" in "indoor and outdoor environments". Future versions of the bugthopter are expected to be able to "perch" in suitable locations, relaying sound and video back to their controllers up to a kilometre away. They might also drop off very small payloads such as listening devices.

“The NAV program will push the limits of aerodynamic and power conversion efficiency, endurance, and maneuverability for very small, flapping wing air vehicle systems,” says Hylton.

It's not immediately clear why an ornithopter like the NAV is better than a tiny helicopter (for instance the Norwegian PD-100 Black Hornet). But DARPA believe that "low Reynolds number"* bird-style flying could offer advantages over normal aircraft technologies.

Even if the idea of pocketsize bug-dropping bugthopter drones never takes off with the US military or intelligence communities, DARPA seems to be suggesting, learning more about exactly how the birds and the bees pull off their tricks is well worth doing. ®

Bootnote

*The Reynolds number is the ratio between inertial forces and viscous forces arising where fluids such as air flow over solid surfaces such as aircraft wings. It is generally high for big, fast things like normal aircraft; but flying critters such as bats and insects operate in low-Reynolds-number flight regimes.